Supplementary Figure 3: Basement membrane and pro-amniotic cavity formation in ETX embryos.

a. Maximum projections from time points indicated showing formation of basement membrane during ETX embryo development. Right-most single-plane images: magnified middle plane of ETX embryo at 108h. Bar=20μm; Representative of 6 ETX embryos for each time point. b. ETX embryo after 3, 3.5, 4 and 5 days showing progression of cavitation. White dashed lines outline the cavity; purple dashed lines outline rosette; boxes, region of magnified inset. Bar=20μm; Representative of 20 ETX embryos for each time point, 4 experiments. c. Progressive formation of the pro-amniotic cavity during ETX embryo development. White boxes indicate magnified inset showing polarised Podxl. Bar=20μm; Representative of 6 ETX embryos for each time point, 2 experiments. d. Quantification of cavities in respective ES and TS-compartments of ETX embryos at days 3, 4 and 5. n=20 ETX embryos per time point. e. ETX embryos during cavitation showing laminin break-down between embryonic and extra-embryonic compartments. Yellow boxes, region of magnified inset. Yellow or black arrowheads indicate break in laminin. Lower panels have laminin staining inverted for better contrast. Black boxes indicate region of zoomed inset. Representative of 20 ETX embryos, 2 experiments. Bar=20μm. f. Quantification of laminin break-down at different developmental time points of ETX embryo embryogenesis. n=20 ETX embryos per time point, 2 experiments.